The bacterial DNA that fossilized in the soil where the Ville-Marie fort was built in 1642 helped reveal certain activities practiced by the first French people who settled in Montreal. These discoveries were made possible thanks to a brand new archaeological approach developed by microbiologists from UQAM in collaboration with the archaeologist from the Pointe-à-Callière museum.
First, the researchers took soil samples from the Ville-Marie fort site, part of which was uncovered and highlighted under a glass floor in a pavilion at the Pointe-à-Callière museum. This fort is the first establishment erected by the founders of Montreal in 1642.
In these samples, microbiologist Cassandre Lazar, professor in the biological sciences department at UQAM, and master’s student Marjorie Collette, had to discriminate between fossil bacteria and living ones. “All living cells contain DNA which is accompanied [d’une copie identique sous forme] of RNA. However, RNA decomposes very quickly, while DNA fossilizes. If we detect DNA which is associated with RNA, this means that this genetic background belongs to a living bacteria. Whereas if we only detect DNA without its associated RNA, that means that this DNA is fossil and belongs to an ancient bacteria,” explained Pointe-à-Callière archaeologist, Hendrik Van Gijseghem, in an interview.
“This is the first time that such a technique has been used on archaeological soils with the aim of shedding light on human activities of the past,” he stressed.
We still have a lot of information gathering and interpretation work to do. […] There is no doubt that bacteria will continue to reveal new information to us.
The fossil bacterial genomes that were identified were then compared to those present in large databases populated by all the world’s microbiologists who transmit their observations, including in particular the precise contexts and environments in which they detected the bacteria that they identified. This is how we were able to know what types of environment or activity the fossil bacteria exhumed from Fort Ville-Marie were associated with.
The most abundant bacterial communities that were detected in the fort first confirmed archaeological observations made previously. “They indicated activities similar to those revealed by archaeological data,” said Mr. Van Gijseghem. For example, the presence of bacterial communities normally associated with rotting meat or butchering activities confirmed that butchery was taking place in the fort.
Tobacco cultivation
The identification of a set of bacteria having been observed, according to the database, in mining waste, as well as in caves of volcanic origin, seemed at first glance very strange to the three researchers. “But bacteria don’t lie, if they are in a place it’s because they really have a reason to be there, because they have very specific environmental preferences,” remarked the archaeologist.
“This bacterial group initially appeared as an anomaly, but we finally put forward the hypothesis of possible blacksmithing and metallurgy work to explain their presence on the site of the fort. Artifacts had been discovered which supported the hypothesis that there had been metallurgical work there. There would have been at least attempts to transform local ore into metal to make tools, and these bacterial communities that we found help to strengthen this interpretation,” he said.
Another discovery for which “the archaeological material available was silent or equivocal” is that of gardening inside the fort. “We know that there were fields of cultivation outside the fort, but we can now imagine that there were small vegetable gardens for market gardening inside the enclosure of the fort, whether for reasons of security or convenience. One of our samples seems to suggest that there was indeed cultivation inside the fort, including the cultivation of tobacco, which is a native plant that was quickly adopted by the French. We knew that they smoked because we had found a lot of pipes, but knowing that it was grown on site was information that was provided to us by the bacteria,” said Mr. Van Gijseghem.
The researchers also found bacteria that had previously been detected on medicinal plants from Asia, which were of course not present in Ville-Marie in the 17th century.e century. “We must be careful in our interpretations because we do not know all the environments in which certain bacteria can be found even though they have been identified in very specific contexts,” he stressed.
“We still have a lot of information gathering and interpretation work to do. […] There is no doubt that bacteria will continue to reveal new information to us,” he said enthusiastically.
The technique requires some effort, but is not particularly expensive, he added. “It could be used to confirm or refute certain hypotheses when the archaeological data is equivocal, imprecise or requires nuance. »
“I see great utility in microbiology, as palynology and entomology have been. It provides new data that contributes to our understanding of the past. As bacteria are everywhere, they will be able to tell us about human activities, but also about the type of vegetation that flourished during these distant times,” he argued.